ISO-7-1 BSPT.pdf

I~tiTERNATIONAL STANDARD

IS0 7-l

Third edition 1994-05-l 5

Pipe threads where pressure-tight joints are made on the threads Part 1: Dimensions, tolerances and designation F&tar de tuyauterie pour raccordement avec Btanch&S dans le Partie 1: Dimensions, tokrances et dksignation

3:45 pm, 6/21/06

Reference number IS0 7-l :1994(E)

IS0 7-1:1994(E)

Foreword IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. IS0 collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard IS0 7-l was prepared by Technical Committee ISOK 5, Ferrous metal pipes and metallic fittings, Subcommittee SC 5, Threaded or plain end butt-welding fittings, threads, gauging of threads. This third edition cancels and replaces the second edition (IS0 7-1:1982), which has been technically revised. IS0 7 consists of the following parts, under the general title Pipe threads where pressure-tight joints are made on the threads: - Part 1: Dimensions, tolerances and designation - Part 2: Verification by means of limit gauges Annex A of this part of IS0 7 is for information only.

0 IS0 1994 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. International Organization for Standardization Case Postale 56 l CH-l 211 Geneve 20 l Switzerland Printed in Switzerland

ii

INTERNATIONAL STANDARD 0 IS0

IS0 7-1:1994(E)

Pipe threads where pressure-tight joints are made on the threads Part 1: Dimensions, tolerances and designation

1 Scope This part of IS0 7 specifies the requirements for thread form, dimensions, tolerances and designation for jointing pipe threads, sizes 1 /I 6 to 6 inclusive, for joints made pressure-tight by the mating of the threads. These threads are taper external, parallel internal or taper internal and are intended for use with pipes suitable for threading and for valves, fittings or other pipeline equipment interconnected by threaded joints. An appropriate jointing medium should be used on the thread to ensure pressure-tight joints. NOTES 1 Parallel external pipe threads are not suitable as jointing threads. 2 For pipe threads where pressure-tight joints are not made on the threads, see IS0 228-l. 3 IS0 7-2 gives details of methods of verification of jointing thread dimensions and form and recommended gauging systems.

2 Normative reference The following standard contains provisions which, through reference in this text, constitute provisions of this part of IS0 7. At the time of publication, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this part of IS0 7 are encouraged to investigate the possibility of applying the most recent edition of the standard indicated below. Members of IEC and IS0

maintain registers of currently valid International Standards. IS0 7-2: 1982, Pipe threads where pressure-tight joints are made on the threads - Part 2: Verification by means of limit gauges.

3 Definitions For the purposes of this part of IS0 7, the following definitions apply (see also figures 3 and 5). 3.1 gauge diameter: Major diameter of the thread, whether external or internal. 3.2 major cone: Imaginary cone which just touches the crests of a taper external thread or the roots of a taper internal thread. 3.3 gauge plane: Plane, perpendicular to the axis of the taper thread, at which the major cone has the gauge diameter. NOTE 4 For external threads the gauge plane is located at a distance equal to the nominal gauge length from the small end of the thread. For internal threads the gauge plane is located at a distance of half-pitch behind the face of the threaded part. This is in order to give consideration to the start of the thread that has been removed by chamfering.

3.4 gauge length: On an external thread, the distance from the gauge plane to the small end of the thread. 3.5 reference plane: Visible surface of each of the internally and externally threaded parts, which facili-

1

IS0 7-1:1994(E)

tates the reading of the gauge when the thread is inspected. For internal threads it is the face of the internally threaded part, for external threads it is the small end of the externally threaded part. 3.6 complete thread: That part of the thread which is fully formed at both crest and root. NOTE 5 When there is a chamfer at the start of the thread not exceeding one pitch in length, this is included in

0

P

Pitch

H

Height of the triangle of the thread profile perpendicular to the thread axis

h

= 0,640 327 P; height of the thread profile between rounded crests and roots perpendicular to the thread axis

r

Radius of rounded crests and roots

D

Major diameter of the internal thread at the gauge plane (gauge diameter - see 3.1)

Dl

D - 1,280 654 P; minor diameter of the internal thread at the gauge plane

the length of complete thread.

3.7 incomplete thread: That part of the thread which is fully formed at the root, but truncated at the crest by its intersection with the cylindrical surface of the product.

IS0

02

D - 0,640 327 P; pitch diameter of the internal thread at the gauge plane

3.8 washout thread; vanish thread: That part of the thread which is not fully formed at the root.

d

Major diameter of the external thread at the gauge plane (gauge diameter - see 3.1)

NOTE 6 The washout thread is produced by the bevel at the start of the threading tool.

d1

= d - 1,280 654 P; minor diameter of the external thread at the gauge plane

3.9 useful thread: Complete thread plus incomplete thread, excluding the washout thread.

4

= d - 0,640 327 P; pitch diameter of the external thread at the gauge plane

3.10 fitting allowance: Length of useful thread beyond the gauge plane of an external thread required to provide for assembly with an internal thread at the upper limit of the tolerance.

T

Tolerance on the gauge length of an external thread

T2

Tolerance for the position of the gauge plane on an internal thread

NOTE 7 Internally threaded parts will have a sufficient length to accommodate the fitting allowance, except when they have a free run-out. See 7.2.2. 3.11 wrenching allowance: Length of useful thread which is provided to accommodate the relative movement between the end of the externally threaded part and the internally threaded part required for wrenching beyond the position of handtight engagement.

5

Dimensions

Pipe thread dimensions, in millimetres, are given in table 1.

6 Designation The designation of threads according to this part of IS0 7 shall consist of the following elements in the sequence given:

4 Symbols Rp

Rc

R

2

Parallel internal pipe thread where pressure-tight joints are made on the threads Taper internal pipe thread where pressure-tight joints are made on the threads Taper external pipe thread where pressure-tight joints are made on the threads

6.1

The description block shall be: Pipe thread

6.2 The International Standard number block shall be: IS0 7

1

3

4

5

6

7

6

10

9

11

Tolerance on position of gauge plane on internal thread

Gauge length (external thread)

Diameters at gauge plane

-

Pitch

Height of thread

Major (gauge diameter)

Pinch

Minor

P

h

d

4

4

Nominal

Tolerance f T,/2

nlSX.

2)

Turns of thread 1

l/16 t/g 114

28 28 19

0,907 0,907 1,337

0,581 0,581 0,856

7.723 9,728 13,157

7,142 9,147 12,301

6,561 8,566 11.445

4 4 6

0.9 03

1

1.3

1

3/g l/2 3/4

19 14 14

1.337 1,814 1,814

0,856 1,162 1,162

16,662 20,955 26,441

15,806 19,793 25,279

14,950 18,631 24,117

6.4 8,2 9.5

1.3 1.8 1.8

1 1 l/4 1 l/2

11 11 11

2,309 2,309 2,309

1,479 1,479 1,479

33,249 41,910 47,803

31,770 40,431 46,324

30,291 38,952 44,845

10.4 12.7 12.7

2.3 2.3 2.3

2 2112 3

11 11 11

2,309 2,309 2,309

1,479 1,479 1,479

59,614 75.164 87,884

58,135 73,705 86,405

56,656 72,226 84,926

15.9 17.5 20.6

2.3 3,5 3.5

4 5 6

11 11 11

2,309 2,309 2,309

1,479 1,479 1,479

113,030 138,430 163,830

111,551 136,951 162,351

110,072 135,472 160,872

25.4 28.6 28.6

3,5 3.5 3.5

20

12

min.

Length of useful external thread not less than

Pitting allowance

Tolerance f T,/2

2)

Turns of thread

21

Turns of thread

Diametral tolerance11 on parallel internal threads

1.7

1 l/4 1 l/4 1 l/4

6.5 6.5 9.7

7,4 7.4 11

5.6 5.6 8.4

2.5 2.5 3.7

2 314 2 3/4 2 3/4

10,071 + 0,071 + 0,104

5.1 6,4 7.7

1.7 2.3 2.3

1 l/4 1 l/4 1 l/4

10.1 13.2 14.5

11.4 15 16.3

8.8 11.4 12.7

3.7 5.0 5.0

2 314 2 3/4 2 314

+ 0,104 $: 0,142 + 0,142

12.7 15.0 15.0

8.1 10.4 10.4

2.9 2.9 2.9

1 l/4 1 l/4 1 l/4

16.8 19,l 19.1

19.1 21.4 21.4

14.5 16.8 16.8

6.4 6,4 6.4

2 314 2 3/4 2 3/4

f 0,180 + 0,180 f 0,180

1

1 l/2 1 l/2

18.2 21 ,o 24,1

13.6 14.0 17.1

2.9 3,5 3.5

1 l/4 1 l/2 1 l/2

23.4 26.7 29.8

25.7 30.2 33.3

21.1 23.2 26.3

7.5 9.2 9-2

31/4 4 4

-+ 0,180 f 0,216 + 0,216

1 l/2 1 l/2 1 l/2

28.9 32,1 32.1

21.9 25,1 25.1

3.5 3.5 3.5

1 l/2 1 l/2 1 l/2

35.8 40,l 40,l

39.3 43,6 43.6

32.3 36.6 36.6

10,4 11.5 11,5

4112 5 5

f 0,216 f 0,216 + 0,216

1.1 l,l

7.3

3.1 3.1 4.7

1 1 1

7,7 10.0 11.3

1 1 1

4.9

4.9

, whi deter1 nestt pitch P, e form h (the height VOTE -The main drmensrons were converted into millimetres on the basis of 1 inch = 25,4 mm, beginning with the number of threads per rr _. __ ~~__ ot thread) = 0.640 327 P and the major drameter at the gauge plane. Patch diameter and manor diameter were then compiled by subtracting once or twice respectively the height of thread h from the major diameter. The nominal gauge length, the tolerances and the fitting allowance were directly computed. The remaining lengths given rn table 1 were obtained by subtracting or adding the tolerances or fitting allowance .espectively to the nominal gauge length. Tolerances and fittrng allowance are expressed in millimetres and in number of turns of thread. 1) For parallel internally threaded parts the diametral tolerances are derived from the tolerances in column 14 by multiplying with the corresponding pitch rn column 3 and with l/16, the amount of taper. 2)

Informative tolerances, in millimetres, are obtained from the mandatory values in turns of thread by multiplying with the corresponding pitch in column 3 and rounding to the nearest 0.1 mm.

0 IS0

IS0 7-1:1994(E)

6.3 a)

The individual item block shall be composed of:

the flanks in such a manner as to give the same thread height h as for parallel threads.

letter symbol(s) for type of pipe thread - the letter R followed by the letter p for parallel internal threads; - the letter R followed by the letter c for taper (conical) internal threads; - the letter R for external threads;

b) the thread size, from column 1 of table 1. EXAMPLES The complete designation for a right-hand thread size 1 l/2: parallel

Pipe thread IS0 7 - Rp 1 l/2

Internal thread

taper

Pipe thread IS0 7 - Rc 1 l/2

External thread

always taper

H = 0,960 491 P h = 0,640 327 P r=O.l37329P

Figure 1 - Parallel thread Pipe thread IS0 7 - R 1 l/2

6.4 For left-hand threads, the letters LH shall be added to the designation. Right-hand threads require no special designation.

7 Thread design

J

Gauge plane

7.1 Thread forms 7.1 .l

Parallel thread

The basic form of the parallel pipe thread shall be as shown in figure 1. The angle between the flanks, measured in an axial plane section, is 55”. The thread profiles are rounded equally at crests and roots by circular arcs blending tangentially with the flanks. 7.1.2 Taper thread The basic form of the taper pipe thread shall be as shown in figure 2. The taper is 1 to 16, measured on the diameter. The angle between the flanks, measured in an axial plane section, is 55”, the flanks making equal angles with the axis. The thread profiles are rounded off equally at crests and roots by circular arcs blending tangentially with

4

H = 0,960 237 P h = 0,640 327 P r=0,137278P

Figure 2 - Taper thread

0

IS0

IS0 7-1:1994(E)

7.1.3 Direction of thread helix Unless otherwise specified, the IS0 7-l thread shall be a right-hand thread. (See also 6.4.)

threads with free run-out shall be not less than 80 % of the values given in column 17 of table 1. (See figure 4.)

8 Gauging 7.2 Thread lengths 7.2.1 External thread The terms relating to the external taper pipe thread are given in figure3. The length of the useful thread, allowable in practice, is the sum of the lengths of the complete and incomplete threads, excluding the washout thread. The minimum length of the useful thread must be not less than the minimum gauge length plus the fitting allowance. 7.2.2 Internal thread The design of internally threaded parts shall be such that they can receive external threads up to the lengths given in column 16 of table 1. The minimum lengths L,i, of useful thread in the case of internal

For the verification of pipe threads, the plug and ring gauges used shall conform to IS0 7-2. The gauging always relates to a reference plane of the threaded part to be verified (see figure5).

9 Combination with fastening thread The combination of an external parallel thread G, tolerance class A or B in accordance with IS0 228-1, with an internal parallel thread Rp in accordance with IS0 7-l needs special consideration. When it is necessary to have this combination, the positive or negative tolerance of the internal thread to IS0 7-1 shall be considered in the relevant product standards, where external parallel threads G are used. Such a combination of threads may not necessarily achieve a leak-tight joint.

Reference plane Useful thread Complete thread

:- Washout Incomplete thread thread

,\\\\\\\\\\\\\\\\\~\\\\\\\\\“\‘\\””””\ ‘0 g;

E Ti

E=

kZ

au

ccl

\

tolerance on internal thread

Figure 3 - Terms relating to external threads

5

IS0 7-1:1994(E)

Free run-out

Free run-out

Figure 4 - Internal threads with free run-out

Internal taper thread Chamfer

c

Useful thread

Reference plane

Gaugeplane

Internal parallel thread

Chamfer

Useful t h r e a d

Reference plane

Gaugeplane

Tolerance for positionof _ (T ,2j gauge plane oninternal + threads Externaltaoerthread

-.-.

Reference plane

c-

Useful thread

.-. + -I

Figure 5 - Illustration of internal and external pipe threads (position of gauge plane, reference plane useful thread)

6

m IS0 7-1:1994(E)

Annex A (informative) Bibliography [I] IS0 228-l :1994, Pipe threads where pressure-tight joints are not made on the threads - Part I: Dimensions, tolerances and designation.

IS0 7-1:1994(E)

ICS 21.040.30 Descriptors: pipe threads, pipe fittings, pipe joints, specifications, Price based on 7 pages

dlmenslons, dimenslonal tolerances, designation, symbols, gauging.